Known is an inverted pendulum type vehicle or an omni-directional vehicle comprising a pair of drive assemblies individually actuated by electric motors and a main wheel held between the drive assemblies and frictionally driven by the drive assemblies. See WO2008132779A1 (US20100096905A1) for instance. Each drive assembly comprises a drive disk coaxially opposing the drive disk of the other drive assembly and a plurality of drive rollers obliquely arranged along the circumference of the drive disk at a regular interval so as to be individually rotatable. The main wheel comprises a ring-shaped annular member rotatably supported by a frame around a central axial line thereof and a plurality of driven rollers arranged along the circumference of the annular member so as to be rotatable around the respective tangential lines. As the drive disks are turned by the electric motors, the driven rollers are frictionally driven by the drive rollers. When the drive rollers are turned around the tangential directions of the main wheel, the vehicle is driven in a lateral direction. When the main wheel is turned around the central axial line thereof, the vehicle is driven in a fore and aft direction. The direction of motion of the vehicle can be selected as desired by suitably adjusting the difference between the rotational speeds of the two drive disks.
In such an inverted pendulum type vehicle, the inverted pendulum control is performed not only with respect to the fore and aft direction but also with respect to the lateral direction. Therefore, when the vehicle occupant (or rider) is improperly seated, typically causing the weight of the vehicle occupant to be unevenly distributed with respect to the lateral direction, the vehicle may travel laterally so as to compensate for the uneven distribution of the vehicle occupant. In particular, when the seat is constructed such that the vehicle occupant cannot readily change the sitting position, the vehicle occupant may have some difficulty in controlling the direction of the movement of the vehicle.